This invention relates to size reduction or comminution machines for reducing the particle size of a given material.
In many industries, for example the pharmaceutical and food industries, it is often desirable to comminute particulate matter, i.e., to reduce the particle size of a given material. Various size reduction processes and machines have been proposed to accomplish the desired result. For example comminution has been accomplished by placing a material on a horizontal sieve and then forcing the material through the sieve with horizontally reciprocating paddles. In a rotating version, such as manufactured by Quadro Engineering, Inc., St. Jacobs, Ontario, Canada, an impeller is rotated within a cylindrical or frusta-conical sieve or fenestrated enclosure, the impeller being belt driven by a motor.
The prior art size reduction machines have six primary draw backs. First, they are difficult to maintain. In many applications, e.g. pharmaceutical and food processing, sterility is most important, thus requiring frequent maintenance of the machinery. With most prior art devices this maintenance function requires substantial disassembly, cleaning and reassembly of the machinery, which is laborious, time-consuming and of course, unproductive.
Second, many prior art devices tend, in large degree, to pulverize the product. In many applications, it is desirable to have a finished product having uniform particle size, without an appreciable amount of fines. Many of the prior art devices have blunt paddles, blades or impellers which overly pulverize the material, resulting in diverse particle sizes and a high percentage of fines in the finished product.
Third, many prior art devices have impellers, set in a fixed position a fixed distance from the sieve. For different materials, it is desirable to adjust the clearance between the impeller and sieve to achieve the desired finished particle size and to maximize production. Prior art devices require the operator to shim the impeller manually in order to change the clearance between the impeller and the sieve, which is laborious and time-consuming.
Fourth, once the impeller-sieve clearance is set, it remains fixed during production. However, production rates could be enhanced if the impeller were allowed to float in relation to the sieve--increasing the clearance when processing a high volume of material and reducing the clearance when processing a small volume of material.
Fifth, the prior art devices do not provide any means for automatically regulating the feed of material into the size reduction machine. This requires an operator to monitor the machine at all times during operation, to regulate the inflow of material into the size reduction machine.
Finally, most prior art devices are belt driven, which increases the complexity of the machine and the difficulty of sanitizing the same, and which is far less energy efficient than direct drive.
It would be desirable to have a size reduction machine that produces a finished product having uniform particle size, is inexpensive, easily maintained, and overcomes the disadvantages of the prior art.